Directional porous coating

ABSTRACT

Porous regions are formed using selected additive manufacturing techniques. The porous regions can assist in fibro-inductive regions and/or osteo-inductive regions. A prosthetic member can be formed completely with the additive manufacturing technique and/or the additive manufacturing techniques can be used to form an augment portion that is added to the prosthetic member formed separately.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/692,127, filed on Aug. 22, 2012. The entire disclosure of the above application is incorporated herein by reference.

FIELD

The subject disclosure is generally related to a structure having a directional and/or directionally biased surface; and particularly to a prosthesis having a porous coating with a directional bias to assist with tissue attachment and pull-out resistance.

BACKGROUND

A prosthesis can be used to replace various portions of an anatomy. In certain instances a subject can be subjected to an injury or disease that wears or causes injury to an anatomical portion. For example, a joint that includes two boney portions that articulate relative to one another can be worn over time. The boney portions that form the joint may be replaced with a prosthesis. The boney portions forming the joint, however, generally have soft tissues connected thereto to assist in movement of the boney portions at the joint. The soft tissues may need to be resected during the implantation procedure that positions the prosthesis. It may be desirable that the soft tissues be reattached to the prosthesis to assist in recreating a substantially natural or original anatomical configuration of the patient.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A prosthesis for a subject, such as a human patient, can be used to replace selected portions of the anatomy. For example, a proximal or distal femur portion that articulate in the hip joint or knee joint can be replaced. Additionally, a proximal tibia or a proximal humerus can be replaced that articulates in a knee or shoulder joint, respectively. The various portions of the anatomy to be replaced can include boney portions that articulate relative to one another at a joint.

The articulation surfaces of boney portions are generally cushioned by cartilage and other soft tissues. In addition, soft tissues, such as tendons and muscles, ensure proper tension and articulation of the boney portions. During a replacement of a joint, such as during resection of a portion of a boney portion and a replacement with a prosthesis, soft tissues may need to be resected or removed from the boney portions. During a replacement with a prosthesis the soft tissue can be reattached to the prosthesis member. For example, extensor mechanisms of the knee, hip, and shoulder can be reattached to the proximal tibia, femur, and humerus respectively.

The prosthesis member can include a surface soft tissue connection region that allows for ingrowth of the soft tissue, also referred to as fibro-inductive, to ensure a connection of the soft tissue over an extended period of time. Auxiliary members can also be used to assist in fixation of the soft tissues. Additionally, the prosthesis members can include a portion that allows for osteo-induction or boney ingrowth to assist in long-term fixation of a prosthesis member within a boney portion. Thus, at least two utilizations can be made independently or in conjunction: 1) increasing pull-out strength of a porous coated device in bone and 2) soft tissue attachment and stabilization.

The fibro-inductive regions and/or osteo-inductive regions can be formed with additive manufacturing using various laser printing or laser sintering techniques. The various additive manufacturing techniques can be used to form the entire prosthetic member for implantation into the boney portion. Alternatively, a prosthetic member can be formed and the additive manufacturing techniques can be used to form an augment portion that is added to the prosthetic member formed separately.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a schematic illustration of a process of forming a prosthesis with an additive manufacturing technique;

FIG. 2A is a perspective view of an acetabular prosthesis, according to various embodiments;

FIG. 2B is a detail view of a portion of the acetabular prosthesis of FIG. 2A;

FIG. 3 is an environmental view of the acetabular prosthesis positioned in an acetabulum;

FIG. 4A is an enlarged view of a surface of the acetabular prosthesis having formed struts, also referred to as bars;

FIG. 4B is a cross-sectional view of the bars of FIG. 4A along line 4A;

FIG. 5 is a schematic view of a proximal femoral prosthesis, according to various embodiments; and

FIG. 6 is a detail view of the prosthesis of FIG. 5 illustrating a soft tissue connection region.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

With reference to FIG. 1, a prosthesis member can be formed with an additive manufacturing technique, including a laser sintering process. Laser sintering processes can be performed by various manufacturers, such as EQS GbmbH electro-optical systems, having a place of business in Munich, Germany or Arcam AB, having a place of business in Mölndal, Sweden. Generally, in a laser sintering process a layer of powder material is laid in a selective thickness that is referred to herein as the sintering layer 10. The powder material can be any appropriate selected material including those discussed herein. The sintering layer 10 can be laid upon pluralities of other layers that are referred to as the base layers 12 herein. The base layers 12 can include one or more of sintering layers 10 that have already been sintered, or at least partially sintered, with a laser 14.

During the laser sintering process, the laser 14 can heat the powder material to a selected temperature to sinter or fix at least a portion of the powder material to powder material provided in a previous layer. During the laser sintering process a plurality of the sintering layers 10 are sequentially laid upon one or more previous layers (i.e. the base layers 12) so that the laser 14 can sinter or fix the current sintering layer 10 to a selected portion of the previous layer. That is, in a previous sintering layer that is now a part of the base layers 12, a particular pattern can have been created by the laser sintering. The current sintering layer 10 can have a pattern sintered with the laser 14 that is sintered and fixed to at least portion of the previously sintered patter in the base layers 12.

An initial member 16 can be formed by layering sintering a plurality of layers together. To form a final member, such as a prosthesis, as discussed further herein, a selected number of sintering layers 10 can be sintered together. Also, additional working can be performed, such as polishing.

During the laser sintering process, the sintering layer 10 can be laid in any selected thickness on the previous layer. The sintering layer 10 can be laid at a thickness generally equivalent to the size of the particles, such as about 0.1 micrometers (μm) to about 1.0 μm. The sintering layer 10 can be provided in any appropriate thickness, including about 50 μm, however, allowing for manufacturing and formation of the final prosthesis or member at a selected rate and other properties.

Generally the laser beam 14 can be directed by a machine and software system to sinter the selected shape in each sintering layer 10. This allows for the formation of the prosthesis in any selected shape that can be formed at a layer at a time. For example, a three dimensional (3D) shape or drawing can be sliced into layers to define the shape to be sintered in each sintering layer 10. By sintering a plurality of the sintering layers the selected final 3D shape can be formed. Also, internal structures can be formed, such as being solid or porous. The finished product can be formed on a scale that is substantially equivalent to the thickness of the sintering layer 10. Accordingly, the final product can have a configuration, internally and externally (such as on an external surface of the final member) that is selected by a designed process.

The design process can be used to design a prosthesis or other selected member in an appropriate configuration. Software, such as computer-aided design software, can be used to design a prosthesis or other selected member with an appropriate internal and external structure. For example, software including design and optimization software can be used to design the internal and external structure of the prosthesis. Exemplary software can include WITHIN ENHANCE optimization software sold by Within Lab, having a place of business in London, United Kingdom.

Additionally, the powder material used in the laser sintering process can be selected from various materials. For example, titanium or titanium alloys can be used in the sintering process. Additionally, cobalt chromium alloys and steel or stainless steel alloys can be used in the sintering process. Various polymers or plastics can also be used in the sintering process such that the metal or polymer materials can be fused or melted together to form a finished product.

With reference to FIGS. 2A and 2B, an acetabular prosthesis 30 is illustrated. The acetabular prosthesis 30 can be formed with the additive manufacturing technique discussed above or include portions that are formed with the additive manufacturing techniques discussed above. The acetabular prosthesis 30 can include an external surface 32 and an internal surface 34. An upper rim 36 can be defined by a thickness between the external surface 32 and the internal surface 34. It is understood that the acetabular prosthesis can include additional features such as an apical hole or other screw fixation holes, as is generally understood in the art.

The external surface 32 of the acetabular prosthesis 30 can additionally include a selected external surface configuration or architecture. The surface architecture can include or be formed as a general roughness in a roughened region 38. The roughened region 38 can include one or more barbs 50 that have a substantially pointed or narrow portion or region 52 at a first end and a wider or broad portion 54 at a second end. The roughened region 38 can generally allow osteo-induction and/or fibro-induction (as discussed further herein). As is generally understood in the art, the acetabular prosthesis 30 can be placed into a prepared acetabulum 60, such as a reamed acetabulum illustrated in FIG. 3, generally in the direction of the Arrow A. That is, the acetabular prosthesis 30 is inserted generally in the direction towards an apical region of the acetabular prosthesis 30.

By insertion of the acetabular prosthesis 30 into the acetabulum in generally the direction of Arrow A, the broad portion 54 of the barbs 50 slide along a surface of the prepared acetabulum. This reduces drag and catching on bone and/or soft tissue. Once the acetabular prosthesis 30 is positioned into the prepared acetabulum in the direction of Arrow A, however, the pointed edge 52 of the barb region 50 can engage the prepared acetabulum, which is generally a boney portion of an anatomy. When the pointed end 52 of the barb 50 engages the boney portion it resists removal of the acetabular prosthesis 30 generally in the direction of Arrow B, which is substantially opposite the direction of Arrow A. The barb 50 can therefore provide a resistance to removal of the acetabular prosthesis 30 from the prepared acetabulum 60.

As illustrated in FIG. 3, the acetabular prosthesis 30 can be positioned in the prepared acetabulum 60 of a pelvis 62 according to generally known techniques. For example, the acetabular prosthesis 30 can be impacted into the acetabulum 60. The barb or plurality of barbs 50 can engage the boney portion of the prepared acetabulum 60 to resist in removal of the acetabular prosthesis from the prepared acetabulum 60.

With particular reference to FIG. 2B, the barbs 50 can be formed to extend from the external surface 32 a selected distance 70. The selected distance 70 can be based upon a manufacturing decision made when designing the acetabular prosthesis 30. During the laser sintering additive manufacturing process, as illustrated in FIG. 1, the barb 50 can be formed to include the designed dimension 70. Accordingly, the distance 70 that the pointed tip 52 may extend from the external surface 32 can be selected from a range of dimensions. For example, the distance 70 can be about 0.1 millimeters (mm) to about 1 mm.

The barb 50, however, can include in the external surface 56 that extends from the pointed portion 52 to the broad portion 54 of the barb 50. The length of the external surface 56 can also have a selected length dimension, such as about 0.1 mm to about 2 mm, including about 0.5 mm. When inserting the acetabular prosthesis 30 generally in the direction of Arrow A, the acetabular prosthesis 30 can move easily into the prepared acetabulum 60 for an implantation procedure. However, the barb 50 can resist removal in your pull-out of the acetabular prosthesis 30 from the prepared acetabulum 60.

Due to the additive manufacturing technique, according to various embodiments, the external surface 32 in the roughened region 38 can also include additional directional or porous lattice configurations. As illustrated in FIG. 2B, a peak or edge 80, or a plurality of the peak or edges 80, can be formed on the external surface 32 of the acetabular prosthesis 30. The peak 80 can be oriented in the same direction as the peak 52 of the macro-bar 50. Thus, the peaks 80 can also reduce possible catching or soft tissue and/or bone during insertion of the prosthesis 30.

The roughened region formed by the peaks or edges 80 can be formed as a strut or bar end portion 82. As discussed herein, struts or bars can be formed with the additive manufacturing technique to form a lattice. The ends of the struts at the end of the prosthesis in the lattice region can form the edges or end portion 82, as illustrated in FIGS. 4A and 4B. The end portions 82 of the struts or bars can act as or form barbs at the roughened surface. As discussed herein, the end portions 82 may also be referred as small or micro-barbs.

Generally, with reference to FIG. 2B, the acetabular prosthesis 30 can include a substantially solid region that is formed as a portion of the thickness of the acetabular prosthesis 30 and generally nearer or starting at the internal surface 34 of the acetabular prosthesis 30. The solid region 84 can form a selected amount of the thickness, including a majority of the thickness, of the acetabular prosthesis 30. A transition region 86 can be formed between the solid region 84 and a lattice portion or region 88 of the acetabular prosthesis 30. The transition region 86 can transition from the solid region 84 to a lattice configuration in the lattice or porous region 88. The lattice configuration can be similar to that illustrated in a lattice formation 89, as illustrated in FIGS. 4A and 4B. Thus, the lattice region 88 can make up an exterior region of the acetabular prosthesis 30.

With reference to FIGS. 4A and 4B, the lattice formation 89 can include a plurality of intersecting struts that are formed as bars or beams, including a main bar 90 and a crossbar 92, in the lattice configuration 89. The main bar 90 or the crossbar 92 can terminate at an external surface of the lattice formation 89 at the external or end portion 82. The end portion 82 can be formed at a selected angle θ. The angle θ can be defined between a central axis of the bars or the edges, as illustrated in FIG. 4B. Regardless, the angle θ can be about 1 degree to about 80 degrees, including about 10 degrees to about 50 degrees, including about 40 degrees. The angle θ can be generally the same for all of the end portions 82 and be formed in general a single selected direction on a selected side or surface of the prosthesis, such as in the direction of Arrow B, as illustrated in FIGS. 2B, 4A, and 4B. The end portion 82 can also be tapered (e.g. as tapering to a point or narrowed region) or can have a width 82 a generally equal to a width of the respective bars 90, 92. The end portions 82 can be formed on the lattice bars 90, 92 at the external surface to generally be in the same direction of the barbs 50. Accordingly, each of the end portions 82 can also resist the removal of the acetabular prosthesis 30 from the boney portion, including the prepared acetabulum 60.

The end portions 82 can resist removal by being configured generally similar to the barbs 50. In other words, the edges 80 can be formed by the end portions 82 such that an edge extends from the exterior surface a selected distance 82 b, such as 0.1 μm to about 1.0 μm, and an elongated surface or portion extends at the angle θ from the exterior surface 32 to the edge. Thus, the end portions 82 can provide a directionality of the roughened region 38 that resists removal of the acetabular prosthesis 30 from the acetabulum 60.

The lattice bars 90, 92 can be formed to generally include a width or thickness 90 a, 92 a of the sintering layer 10 or a multiple of the sintering layers 10. Accordingly, the thickness of the lattice bars 90, 92 can be about 0.1 μm to about 1 millimeter (mm), including about 1 μm to about 500 μm. Accordingly, the end portions 82 can be referred to as microbarbs or small barbs that have the dimensions of one of the lattice bars, such as about 0.1 μm to about 1 millimeter (mm), including about 1 μm to about 500 μm. The microbarbs may have a dimension that is a multiple of a size of the material or material layers used to form the lattice bars 90, 92. As illustrated and disclosed here, the micro- or small barbs are generally defined by a single one of the bars 90, 92. The barbs 50 can be referred to as macro-barbs or large barbs. As illustrated and disclosed here, the macro- or large barbs are generally defined by a size greater than a single one of the bars 90, 92.

Further, the entire exterior surface 32 of the acetabular prosthesis 30 can be formed with the microbarbs 82, including the exterior surface 56 of the barbs 50. Accordingly, the exterior surface 32 of the acetabular prosthesis 30 can be formed to include a configuration that resist removal of the acetabular prosthesis 30 generally in the direction of Arrow B. It is further understood, however, that the acetabular prosthesis 30 can have attached thereto an augment or member that is formed with the lattice formation 89. For example, the acetabular prosthesis 30 can include a pocket into which the augment is fixed, such as by welding, sintering, or adhesion, or other appropriate fixation technique.

The lattice formation or structure 89, as illustrated in FIGS. 4A and 4B, having the end portions 82 and the lattice bars 90, 92, can form open or porous areas 100 between the lattice bars 90, 92 and the end portions 82. The pores can be formed in the external portion of the bars 90, 92 or can be formed a selected distance into the lattice structure. Accordingly, the porous region 88 can allow for boney ingrowth or osteoinduction that assists in fixation of the acetabular prosthesis 30 within the pelvis 62. The end portions 82 and the barbs 50 can assist in the induction by resisting initial removal and movement of the acetabular prosthesis 30, generally in the direction of Arrow B.

In addition to boney ingrowth, as illustrated in FIGS. 2A-3 above the barbs 50 and end portions 82 can be used to allow for soft tissue fixation at soft tissue regions, such as with soft tissue ingrowth or fibro-induction. With reference to FIG. 5 a proximal femoral prosthesis 150 is illustrated. The proximal femoral prosthesis 150 can include a stem portion 152 and a body portion 154 that includes a neck 156. The neck 156 can include a taper or other meeting portion to engage or mate with a femoral head 160. The prosthesis 150 can generally include a longitudinal axis 164 that extends along the longitudinal axis of the body portion 154 and the stem portion 152. The body portion 154 and the stem portion 152 can be formed as a single member or can be formed separately and allow for interconnection during implantation. If the body portion 154 is formed separately from the stem portion 152 a connection portion 170 can be provided or formed to allow for interconnection and fixation of the body portion 154 relative to the stem portion 152.

The stem portion 152 can also be formed using the additive manufacturing techniques, including laser sintering as illustrated in FIG. 1. Accordingly, the stem portion 152 can include a substantially solid region 180, a transition region 182, and the lattice or porous region 184. Generally, the regions extend from a center to an outer surface of the stem. Thus, the center of the stem, generally near the central axis 164, is solid while the outer surface includes the porous region 184.

The porous region 184 can include one or more barbs 186 similar to the barbs 50 illustrated above. It is understood, however, that the barbs 186 can be formed on the exterior of the stem 152, whether the outer surface is porous or non-porous. The barbs 186 can be orientated to reduce risk of catching soft tissue and/or bone during insertion of the prosthesis 150, but can resist removal and withdrawal of the stem 152 once implanted. As discussed above, the additive manufacturing techniques can be used to make solid members that are substantially pore free as well. The barbs 186 can assist in bone fixation of the prosthesis 150 once the stem portion 152 is inserted into a selected boney portion, such as a proximal femur.

Additionally, the porous region 184 can include the end portions 82 (e.g. the micro-barbs) or similar configuration at the external surface of the stem 152 to assist in fixation of the stem portion 152 to a boney member or a portion. The end portions 82 can be formed to angle generally in a direction towards the neck 156. Thus, the porous region can include a directionality to resist movement of the stem 152 from the bone 190 while reducing possible catching of the stem 152 on soft tissue/and or bone during implantation of the stem 152.

The porous region including the micro-barbs and pores formed due to the lattice configuration, as illustrated in FIGS. 4A and 4B, can allow for osteo-induction into the porous region of the stem 152. Accordingly, the stem member 152 can be fixed into a boney portion, such as the femur 190 in according to selected implantation techniques. In addition adhesive or bone cement can be used to assist in fixation and the barbs 186 and end portions 82 can assist in adhesion of the cement. It is understood, however, that adhesives are not necessary and that osteo-induction may be increased when an adhesive is not used, thus allowing for a direction contact of the natural bone surface and the roughened region 38.

In addition to honey fixation at the exterior region of the stem portion 152 or on the exterior surface 32 of the acetabular prosthesis 30, soft tissue can be attached to a selected prosthesis portions. With continuing reference to FIG. 5, a soft tissue connection region 200 can be formed on the body portion 154 of the prosthesis 150. The soft tissue connection region 200 can include a solid region 202, a transition region 204, and a porous or lattice region 206. Similar to the various layers, including the solid 180, the transition 182, and the porous or lattice layer 184, the layers of the soft tissue connection region 200 can be used to allow for fixation of soft tissue to the body region 154.

The lattice or porous region 206 of the soft tissue connection region 200 can include the lattice structure 89 as illustrated in FIGS. 4A and 4B. Accordingly, the porous region 206 can include the end portions 82 that are formed in a direction to allow for fixation or holding of soft tissue relative to the body portion 154. As is generally understood, a hip extensor soft tissue portion may be removed from a proximal femur, such as a greater trochanter of the femur 190, during a proximal femur resection. To allow for substantially anatomical reconfiguration of the anatomy after implantation of the prosthesis 150, the hip extensor can be reconnected to the soft tissue connection region 200 to substantially mimic connection to a greater trochanter in the natural or original anatomy. The soft tissue can be connected to the soft tissue connection region 200 due to the end portions 82 of the porous region 206. The end portions 82 in the porous region 206 can all be formed to have ends, which may also taper relative to the respective bars 90, 92, that extend distally (i.e. away from) from the origin of the hip extensor. In other words, the end portions 82 can be angled generally in the direction of arrow C, illustrated in FIG. 5. Thus, the porous region 206 can have a directional resistance to movement of tissue contacting the porous region 206.

In addition to or in combination with the end portions 82, optional macrobarbs barbs 210 can also be formed in the soft tissue connection region. The macrobarbs 210 can include dimensions similar to the macro barbs 50, discussed above. The macrobarbs, 210, therefore, can include narrow ends that are also angled in the direction of Arrow C. The end portions 82 of the lattice region, 206 either a bone or in combination with the macrobarbs 210 on the soft tissue connection region 200, can allow for a connection of soft tissue. Thus, the soft tissue connection region 200 can offer a substantially permanent long term fixation of the soft tissue.

In addition, it is understood that an optional washer and screw fixation system 220, including a washer or barbed washer 222 and a screw 224, similar to the WasherLoc™ tibial fixation device sold by Biomet, Inc., can be used to engage soft tissue into the body portion 154 of the prosthesis 150. Generally the spiked washer 222 can engage the soft tissue and spikes thereof can pierce or fixedly engage the soft tissue. Also, the portions of the screw fixation system 220 can also be formed to include the barb or micro-barb structure. For example, an external surface of the spiked washer can include the microbarb structure.

The screw 224 can be threaded into and engage a bore, such as a blind bore 230, in the body portion 154 of the prosthesis 150. The washer and screw assembly 220 can allow for an initial fixation of soft tissue to the prosthesis 150 while the macrobarb 210 and the lattice portion or region 206 of the soft tissue connection region 200 allows for substantially permanent fixation and ingrowth of the soft tissue. As discussed above, the porous region 100 of the lattice region 206 can allow for soft tissue ingrowth into the body member 154 to provide for substantially a long-term fixation soft tissue to the prosthesis 150.

As illustrated in detail in FIG. 6 a soft tissue portion 250, including a hip extensor, can be engaged to the soft tissue connection region 200. In FIG. 6 the lattice structure including the struts 90, 92 are shown to detail the configuration thereof and the interaction of the struts 90, 92 with the soft tissue portion 250. It is understood, however, that the struts 90, 92 may not be shown to scale. As discussed above, the struts may have a diameter of less than one millimeter.

The soft tissue portion 250 can engage the microbarbs 82 formed by the ends of the bars 92 that are all angled in substantially a similar direction. The soft tissue portion 250 then can have a force, when acting on the prosthesis 150, which is generally in the direction of arrow D. As illustrated, the direction of the force D can be substantially transverse, including substantially perpendicular, to the microbarbs 82, where dashed line 82 c illustrates the position of the microbarbs 82.

It is understood that other prosthetic members can be formed to include the porous lattice region, such do the porous region 206 for soft tissue ingrowth and the porous region 184 for boney ingrowth. For example, stem or bone contacting portions of a proximal humeral replacement or proximal tibial replacement can be provided with porous regions as discussed above. Additionally, soft tissue connection regions can be provided on tibial prosthetic members and humeral prosthetic members to allow for soft tissue attachment of the patellar tendons, knee extensors, and/or rotator cuff tendons.

Accordingly, the specific examples illustrated above are not exclusive of other possible prosthesis that can include the barbed end 82 or the macrobarbs, such as the macrobarb 210. Accordingly, various prosthetic members can include both boney ingrowth regions formed with the lattice structures including macro and micro fixation portions.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A method of forming a prosthesis, comprising: forming a plurality of substantially uniformly oriented strut ends of a lattice structure at a surface of the prosthesis, wherein the strut ends are angled relative to a remainder of a length of a strut of the lattice structure. 